Cytotoxic stilbene derivatives and pharmaceutical composition containing them

Abstract: Stilbene derivatives of the following general formula (1) or their pharmaceutically acceptable acid addition salts are low in toxicity, but are water soluble and effective as carcinostatics: wherein R¹, R² and R³ each represent an alkyl group having 1 to 3 carbon atoms; X represents a hydrogen atom or a nitrile group; and Y represents an alkyloxy group having 1 to 3 carbon atoms, an alkyl group having 1 to 6 carbon atoms or a halogen atom.

Description: The present invention relates to cis-stilbene derivatives, to their use as pharmaceuticals and, in particular, to carcinostatics containing them as active ingredients. Combretastatins having cis-stilbene as their basic skeleton are known to have strong cytotoxicity. However, because they are barely soluble in water, they have not been put to practical use as medicines. Therefore, various investigations to develop their derivatives have been made (Molecular Pharmacology 34 , 200-206 (1988); J. Med. Chem., 34 , 2579-2588(1991); WO 92/16486; J. Med. Chem., 35 , 2293-2306(1992); WO 93/23357; J. Med. Chem., 36 , 2817-2821(1993); Bioorg. Med. Chem. Let., 4 , 699-704(1994)), but compounds,which are effective in vivo are still unknown. The present inventors sought to identify combretastatin derivatives which may be synthesized easily, which are of low toxicity and which have a high pharmaceutical effect, and to provide carcinostatics containing them. The present inventors synthesized various stilbene derivatives and screened carcinostatic compounds from them and, as a result, found that compounds of the following general formula (1) have a remarkable carcinostatic effect in vivo. These compounds, which have an amino group at the 3-position of the benzene ring of cis-stilbene, are novel combretastatin derivatives wherein X represents a hydrogen atom or a nitrile group. Examples of compounds of the invention include, for example, the following: (Z)-1-(3-amino-4-methoxyphenyl)-2-(3,4,5-trimethoxyphenyl)ethene, (E)-3-(3-amino-4-methoxyphenyl)-2-(3,4,5-trimethoxyphenyl)-prop-2-en-nitrile, Compounds of formula (1) of the present invention may be produced, for example, according to the reaction route mentioned below. In these formulae, R 1 , R 2 , R 3 are all methyl groups and Y is a methoxy group. In these formulae, R 1 , R 2 , R 3 and Y have the same meanings as those mentioned above. Precisely, compounds of formula (5) which belong to the compounds of the present invention may be obtained, for example, by reacting a triphenylphosphine bromide derivative of formula (2) and an aldehyde of formula (3) at room temperature in alcohol or benzene, in the presence of a base such as sodium hydride or sodium ethoxide for 2 to 4 hours followed by subjecting the reaction product to chromatography to obtain the intended cis-compound. The cis-compound may be reduced with zinc-acetic acid or the like to obtain a compound of formula (5). Compounds of formula (10) which belong to the compounds of the present invention may be produced, for example, by reacting a phenylacetonitrile derivative (6) and an aldehyde derivative (7) in dichloromethane in the presence of sodium hydroxide for 2 to 4 hours, obtaining the cis-compound (9) by photo-isomerising the trans-compound (8) followed by reducing the cis-compound (9) with a reducing agent such as zinc-acetic acid. The stilbene derivatives of the present invention that have been produced according to the above-mentioned method may easily be separated and purified from the reaction mixtures by ordinary isolating and purifying means, for example, by extraction with solvents, chromatography, crystallization. Where the above-mentioned stilbene derivatives are used as carcinostatics, they are administered to patients perorally or parenterally (for example, by intramuscular injection, subcutaneous injection or intravenous injection or as suppositories). Their dose varies, depending on the symptoms of patients. In general, it may be from 1 to 9000 mg/adult/day and is divided into parts of from 1 to 3000 mg each to be administered to patients several times a day. Where the stilbene derivatives of the present invention are formulated into peroral preparations, a vehicle and optionally other additives such as binder, disintegrator, lubricant, colorant, flavoring are added thereto and the resulting mixtures are formed into tablets, coated tablets, granules, capsules by ordinary methods. As the vehicle, for example, usable are lactose, corn starch, white sugar, glucose, sorbitol, crystalline cellulose. As the binder, for example, usable are polyvinyl alcohol, polyvinyl ether, ethyl cellulose, methyl cellulose, arabic gum, tragacanth, gelatin, shellac, hydroxypropyl cellulose, hydroxypropyl starch, polyvinyl pyrrolidone. As the disintegrator, for example, usable are starch, agar, gelatin powder, crystalline cellulose, calcium carbonate, sodium hydrogencarbonate, calcium citrate, dextran, pectin. As the lubricant, for example, usable are magnesium stearate, talc, polyethylene glycol, silica, hardened vegetable oils. As the colorant, for example, usable are colorants that have been accepted as those applicable to medicines. As the flavoring, for example, usable are cocoa powder, menthol, aromatic acids, peppermint oil, borneol, cinnamon powder. As a matter of course, these tablets and granules may optionally be coated, for example, with sugar coats, gelatin coats. Where the stilbene derivatives of the present invention are formulated into injections, a pH-adjusting agent, a buffer, a stabilizer, a preservative may optionally be added thereto and formed into subcutaneous, intramuscular or intravenous injections by ordinary methods. The stilbene derivatives of the present invention may optionally be formed into their pharmaceutically-acceptable acid-addition salts with inorganic acids such as hydrochloric acid, sulfuric acid, phosphoric acid, and with organic acids such as oxalic acid, fumaric acid, maleic acid, malic acid, citric acid, tartaric acid, glutamic acid. Examples The present invention will be explained in detail by means of the following examples, which, however, are not intended to restrict the scope of the present invention. Example 1: Preparation of (Z)-1-(3-amino-4-methoxyphenyl)-2-(3,4,5-trimethoxyphenyl)ethene: Step 1: Preparation of (Z)-1-(3-nitro-4-methoxyphenyl)-2-(3,4,5-trimethoxyphenyl)ethene: 1.54 g of 3-nitro-4-methoxybenzaldehyde and 4.45 g of 3,4,5-trimethoxybenzyltriphenylphosphine bromide were dissolved in 40 ml of benzene, and a benzene solution containing 408 mg of sodium hydride dispersed therein was added thereto and reacted for 15 hours at room temperature. The reaction mixture was neutralized with acetic acid, saturated saline solution was added thereto, and the resulting liquid was extracted with dichloromethane. The extract was dried with anhydrous sodium sulfate, concentrated and then purified by silica gel column chromatography (ethyl acetate:hexane = 1:2) to obtain 1.27 g of the intended compound. The yield of the product was 43 %. 1 H-NMR (CDCl 3 ):7.79(1H, d, J=2.1), 7.42(1H ,dd J=2.1 ,8.7 ), 6.93(1H, d, J=8.7), 6.58(1H, d, J=12.9), 6.47(2H, s), 6.44(1H, d, J=12.9), 3.93(3H, s), 3.85(3H, s), 3.71(6H ,s); mass spectrum (m/z):345(M + ) Step 2: Production of (Z)-1-(3-amino-4-methoxyphenyl)-2-(3,4,5-trimethoxyphenyl)ethene: 700 mg of (Z)-1-(3-nitro-4-methoxyphenyl)-2-(3,4,5-trimethoxyphenyl)ethene were dissolved in 35 ml of acetic acid, and 7 g of zinc were added thereto and stirred for one hour. The reaction liquid was filtered, concentrated and purified by silica gel column chromatography (dichloromethane:hexane = 2:1) to obtain 314 mg of the intended compound. Its yield was 49.3 %. 1 H-NMR(CDCl 3 ):6.69(1H, s), 6.67(2H, s), 6.55(2H, s), 6.45(1H, d, J=12.0), 6.36(1H, d, J=12.O), 3.84(3H, s), 3.82(3H, s), 3.69(6H, s); mass specturm (m/z):315(M + ) Example 2 Production of (E)-3-(3-amino-4-methoxyphenyl)-2-(3,4,5-trimethoxyphenyl)-prop-2-ene-nitrile: Step 1: Production of (Z)-3-(3-nitro-4-methoxyphenyl)-2-(3,4,5-trimethoxyphenyl)-prop-2-ene-nitrile: 3.0 g of 3-nitro-4-methoxybenzaldehyde, 3.4 g of 3,4,5-trimethoxyphenylacetonitrile, 800 mg of sodium hydroxide and 100 mg of octylmethylammonium chloride were dissolved in 15 ml of water and 15 ml of dichloromethane and reacted for 4 hours at room temperature. Ice water was added to the reaction liquid, which was then extracted three times each with dichloromethane. The extract was dried with anhydrous sodium sulfate and concentrated. The concentrated liquid was purified by crystallization (ethyl acetate) to obtain 4.4 g of the intended compound. Its yield was 72 %. 1 H-NMR(CDCl 3 ):8.30(1H, dd, J=2.4, J=9.0), 8.21(1H, d, J=2.4), 7.38(1H, s), 7.21(1H, d, J=9.0), 6.86(2H, s), 4.05(3H, s), 3.94(6H, s), 3.89(3H, s); mass spectrum (m/z):370(M + ); melting point 191-192°C Step 2: Production of (E)-3-(3-nitro-4-methoxyphenyl)-2-(3,4,5-trimethoxyphenyl)-prop-2-ene-nitrile: 2.0 g of (Z)-3-(3-nitro-4-methoxyphenyl)-2-(3,4,5-trimethoxyphenyl)-prop-2-ene-nitrile were dissolved in 500 ml of acetonitrile and exposed to visible light rays for 60 minutes. The reaction liquid was concentrated and crystallized from ethyl acetate to obtain 996 mg of the intended compound. Its yield was 49 %. 1 H-NMR(CDCl 3 ):7.74(1H, d, J=2.1), 7.35(1H, dd, J=2.1, 9.0), 7.19(1H, s), 6.94(1H, d, J=9.0), 6.58(2H, s), 3.95(3H, s), 3.89(3H, s), 3.78(6H, s); mass spectrum (m/z):370(M + ); melting point 158-159°C Step 3: Production of (E)-3-(3-amino-4-methoxyphenyl)-2-(3,4,5-trimethoxyphenyl)-prop-2-ene-nitrite: 500 mg of (E)-3-(3-nitro-4-methoxyphenyl)-2-(3,4,5-trimethoxyphenyl)-prop-2-ene-nitrite were dissolved in 25 ml of acetic acid, and 5 g of zinc were added thereto and stirred for 30 minutes at room temperature. The reaction liquid was filtered and then concentrated. The concentrated liquid was purified by silica gel column chromatography (ethyl acetate:hexane = 1:2) to obtain 457 mg of the intended compound. Its yield was 99 %. 1 H-NMR(CDCl 3 ):7.26(1H, s), 7.16(1H, s), 6.65(2H, s), 6.64(1H, s), 6.56(1H, s), 3.88(3H, s), 3.84(3H, s), 3.77(6H, s); mass spectrum (m/z):340(M + ); melting point 144-145 ° C Example 3 : Cytotoxicity test: Mouse P388 leukemia cells were used as cancer cells for the test. The cancer cells were incubated in RPMI-1640 medium containing 5 µM 2-mercaptoethanol and 10 % fetal calf serum. Precisely, the cancer cells were seeded in a 96-well microplate in an amount of 1 x 10 4 cell/50 µl/well, 25 µl/well of an aqueous solution of the test compound mentioned below (4 pg/ml) were added to each well, and the cells were incubated therein for 2 days at 37 °C. After the incubation, the number of the living cells was counted by MTT method and a dose-reaction curve was formed from the counted data. Based on the curve, the 50 % growth-inhibiting concentration (IC 50 ) of the test compound was calculated. The IC 50 value of each compound is shown in Table 1. As a comparative compound, Combretastatin A-4 was used. As is noted from Table 1, the compounds of the present invention each have IC 50 value comparable to that of Combretastatin A-4. Example 4: Evaluation of Antitumor Activity: Colon 26 was inoculated sc into CD2F1 mice. After a week, the size of tumor was measured and the volume of the tumor was calculated. Mice were selected on the volume of the tumor and administration of drug was began. After 21 days from the day of administration, the size of the tumor was measured and the volume of tumor was calculated. I.R.(Inhibition ratio of growth of tumor) was calculated as below. I.R.(%)={1-(average tumor volume of treated mice)/(average tumor volume of control mice)}x100 The inhibition ratios are shown in Table 1. Example 5: Solubility: Excess amount of each sample was dissolved in 0.1ml of phosphate buffer (PH 7.0). The mixture was sonicated and centrifuged. The supernatant was subjected to HPLC and the solubility was measured. Results are shown in Table 2.

Claims: A compound having the formula wherein x is H or CN or a pharmaceutically acceptable acid addition salt thereof. A compound according to preceding claim 1 for pharmaceutical use. A carcinostatic composition comprising a compound of claim 1 and a pharmaceutically acceptable excipient, diluent, or carrier. Use of a compound of claim 1 in the manufacture of a carcinostatic. A method for the production of a compound as defined in claim 1, comprising reduction of the nitro group of a compound of formula (1A) wherein X is H or CN. A compound of formula (1A) wherein X is H or CN.

Inventors: MORINAGA YOSHIHIRO, OHISHI KAZUO, OHSUMI KOJI, TSUJI TAKASHI, MORINAGA, YOSHIHIRO, OHISHI, KAZUO, OHSUMI, KOJI, TSUJI, TAKASHI, Morinaga, Yoshihiro c/o Centr. Research Lab., Ohishi, Kazuo c/o Centr. Research Lab., Ohsumi, Koji c/o Centr. Research Lab., Tsuji, Takashi c/o Centr. Research Lab.
Applicants: AJINOMOTO KK, AJINOMOTO CO., INC.
Application year: 1994
Main classification: C07C217
IPC codes: C07C205, C07C217, C07C255